Network services which enable users of the service to share content are well known. For example social networking services which enable users to make contacts, and exchange messages and other content with other users are well known. A user of such a service may store content at a server and permit other users to the service to access the content.
Such network services may be subscriber services and require a user to register with the service provider.
The content may comprise text, for example, blogs which have been created by the user or messages which have been received from other users of the service. The content may also comprise images or audio files such as music files or media files such as video files.
A user of the network service may be able to control the access rights to their content. For example they may be able to control who can access their content and the level of access other users have to their content.
It is advantageous for users of such services to be able to easily but securely change the access rights associated with their content. For example they may meet a new person and would like to permit that new person to access their content.